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Question: Answered & Verified by Expert
\({ }_{98} \mathrm{Cf}^{246}\) was formed along with a neutron when an unknown radioactive substance was bombarded with \({ }_{6} \mathrm{C}^{12}\). The unknown substance was :
ChemistryChemical KineticsWBJEEWBJEE 2014
Options:
  • A \({ }_{91} \mathrm{~Pa}^{234}\)
  • B \({ }_{90} \mathrm{Th}^{234}\)
  • C \({ }_{92} \mathrm{U}^{235}\)
  • D \({ }_{92} \mathrm{U}^{238}\)
Solution:
2522 Upvotes Verified Answer
The correct answer is: \({ }_{92} \mathrm{U}^{235}\)
Let, the unknown radioactive substance be ${ }_{x} A^{y}$.
$x A^{y}+{ }_{6} C^{12} \longrightarrow{ }_{98} C f^{246}+{ }_{0} n^{1}$
On comparing atomic numbers, we get
$$
\begin{array}{r}
x+6=98+0 \\
x=98-6=92
\end{array}
$$
On comparing mass numbers, we get
$$
y+12=246+1
$$
$$
\begin{aligned}
y &=247-12 \\
&=235
\end{aligned}
$$
Since, uranium has the atomic number 92 , thus, the given unknown substance was ${ }_{92} \mathrm{U}^{235}$.

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